1. Field of the Invention
This invention relates to photosensor arrays and more particularly to a photosensor array encapsulated in a housing arranged to be relatively insensitive to undesired reflections.
2. Description of the Prior Art
Referring to FIG. 1 there is shown a cross-sectional view of a prior art self-scanned photosensor array 10 of the type used in high quality image detecting applications. The array 10 includes a plurality of photosensors, such as known photodiodes, deposited on a dielectric substrate 11. Each of the photosensors produces a photoelectric effect in response to an incident beam of light. The array 10 and associated integrated electrical circuitry are usually encapsulated in a plastic case 14 equipped with external connecting means 12 and covered with a sheet of transparent material 16, such as glass. A cavity or space 18 is formed between a back surface 20 of the glass cover 16 and the array 10. As a result of this construction, first 22 and second 24 glass-air interfaces are provided. When light rays from an image are incident on a front surface 26 of the glass cover 16 at an angle, the rays are refracted, and some reflection occurs at both the front surface 26 of the glass cover 16 and the array 10 itself. The light not absorbed by the array 10 is reflected to the back surface 20 of the glass cover 16 where it is again subject to a combination of penetration and reflection. Multiple reflections or flare can occur to cause an appreciable amount of light to be scattered within the case 14, and impair the resolution capabilities of an image scanning system comprising the array 10 to produce images of apparent reduced contrast.
Accordingly, it is an important object of the invention to provide a photosensor array with improved resolution.
It is another object of the invention to achieve the preceding object with apparatus that is relatively inexpensive, compact and reliable.